Method for manufacturing memory device

ABSTRACT

A method includes depositing a bottom electrode layer, a resistance switching element layer, and a top electrode layer over a first dielectric layer; etching the top electrode layer and the resistance switching element layer to form a resistance switching element over the bottom electrode layer and a top electrode over the resistance switching element; depositing a metal-containing compound layer over the top electrode, the resistance switching element, and the bottom electrode layer; and etching the metal-containing compound layer and the bottom electrode layer to form a bottom electrode over the first dielectric layer.

PRIORITY CLAIM AND CROSS-REFERENCE

This application is a divisional application of U.S. patent applicationSer. No. 15/706,709, filed Sep. 16, 2017, now U.S. Pat. No. 10,461,246,issued Oct. 29, 2019, which is herein incorporated by reference in itsentirety.

BACKGROUND

Semiconductor memories are used in integrated circuits for electronicapplications, including radios, televisions, cell phones, and personalcomputing devices, as examples. One type of semiconductor memory deviceinvolves spin electronics, which combines semiconductor technology andmagnetic materials and devices. The spins of electrons, through theirmagnetic moments, rather than the charge of the electrons, are used toindicate a bit.

One such spin electronic device is magnetoresistive random access memory(MRAM) array, which includes conductive lines (word lines and bit lines)positioned in different directions, e.g., perpendicular to each other indifferent metal layers. The conductive lines sandwich a magnetic tunneljunction (MTJ), which functions as a magnetic memory cell.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1A through 1M are cross-sectional views of an integrated circuitin various stages of fabrication in accordance with some embodiments ofthe present disclosure.

FIGS. 2A through 2B are cross-sectional views of an integrated circuitin various stages of fabrication in accordance with some embodiments ofthe present disclosure.

FIG. 3 is a cross-sectional view of an integrated circuit in accordancewith some embodiments of the present disclosure.

FIG. 4 is a cross-sectional view of another integrated circuit inaccordance with some embodiments of the present disclosure.

FIG. 5 is a cross-sectional view of another integrated circuit inaccordance with some embodiments of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

A magnetic random-access memory (MRAM) device and the method of formingthe same are provided in accordance with various exemplary embodiments.The intermediate stages of forming the MRAM device are illustrated. Thevariations of the embodiments are discussed. Throughout the variousviews and illustrative embodiments, like reference numbers are used todesignate like elements.

FIGS. 1A through 1M are cross-sectional views of an integrated circuit(IC) in various stages of fabrication in accordance with someembodiments of the present disclosure. FIG. 1A illustrates a waferhaving a substrate 100 thereon. The substrate 100 includes an interlayerdielectric (ILD) layer or inter-metal dielectric (IMD) layer 110 withmetallization pattern 112. The ILD layer 110 may be an extra low-kdielectric (ELK) layer, such as carbon doped silicon dioxide, may be anoxide, such as silicon oxide, and/or may be the like or a combinationthereof. In some embodiments, the ILD layer 110 may be formed of a low-kdielectric material having a k value less than about 3.9. The k value ofthe ILD layer 110 may even be lower than about 2.8. The metallizationpattern 112 may be copper, aluminum, the like, and/or a combinationthereof. The substrate 100 may also include active and passive devices,for example, underlying the ILD layer 110. These further components areomitted from the figures for clarity, and how these components areformed will be readily apparent to a person having ordinary skill in theart.

A bottom electrode layer 120 is formed over the ILD layer 110. Thebottom electrode layer 120 may be formed of conductive materials, suchas copper, aluminum, tantalum, tungsten, tantalum nitride (TaN),titanium, titanium nitride (TiN), the like, and/or a combinationthereof. The bottom electrode layer 120 may be a single-layeredstructure or a multilayered structure. For example, the bottom electrodelayer 120 may include a tantalum nitride layer and a titanium nitridelayer over the tantalum nitride layer. In some embodiments, the bottomelectrode layer 120 has a thickness in a range from about 50 angstromsto about 1000 angstroms. The bottom electrode layer 120 can be formedusing suitable deposition techniques, such as chemical vapor deposition(CVD), physical vapor deposition (PVD), atomic layer deposition (ALD),the like, and/or combinations thereof.

Stacks 130 are then formed over first portions 122 of the bottomelectrode layer 120 respectively. Each of the stacks 130 includes aresistance switching element 132 and a top electrode 134 over theresistance switching element 132. Regarding the formation of the stacks130, a resistance switching element layer and a top electrode layer maybe formed in sequence on the bottom electrode layer 120, and then bepatterned into the resistance switching element 132 and the topelectrode 134. The resistance switching element layer and the topelectrode layer may be formed using suitable deposition techniques, suchas CVD, PVD, ALD, the like, and/or combinations thereof. In someembodiments, the resistance switching element 132 may include a magnetictunnel junction (MTJ) structure including various layers formed ofdifferent combinations of materials. In some exemplary embodiments wherethe resistance switching element 132 includes the MTJ structure, it mayinclude a pinning layer 132 a, a tunnel barrier layer 132 b, and a freelayer 132 c. In addition, the MTJ structure may have other variationsincluding other layers, such as anti-ferro-magnetic layers. In someembodiments, the pinning layer 132 a is formed of PtMn, the tunnelbarrier layer 132 b is formed of MgO, and the free layer 132 c is formedof CoFeB. The magnetic moment of the free layer 132 c may be programmedcausing the resistance of the resulting MTJ cell to be changed between ahigh resistance and a low resistance. In some embodiments, the topelectrode 134 may be formed of conductive materials, such as copper,aluminum, tantalum, tungsten, tantalum nitride (TaN), titanium, titaniumnitride (TiN), the like, and/or a combination thereof.

In some embodiments where resistive random access memory (RRAM) cellsare to be formed on the wafer, the resistance switching element 132 mayinclude a RRAM dielectric layer such as metal oxide composite, such ashafnium oxide (HfO_(x)), zirconium oxide (ZrO_(x)), aluminum oxide(AlO_(x)), nickel oxide (NiO_(x)), tantalum oxide (TaO_(x)), or titaniumoxide (TiO_(x)) as in its relative high resistance state and a metalsuch as titanium (Ti), hafnium (Hf), platinum (Pt), ruthenium (Ru),and/or aluminum (Al) as in its relative low resistance state.

Reference is made to FIG. 1B. A first spacer layer 140 is blanket formedover the bottom electrode layer 120 and over sidewalls and top surfacesof the stacks 130. The first spacer layer 140 may include suitabledielectric materials such as silicon nitride, silicon carbide,carbon-doped silicon nitride, carbon-doped silicon oxide, siliconoxynitride, and combinations thereof. In some embodiments, the firstspacer layer 140 may also be a composite layer including two or morelayers made of different materials, such as a silicon nitride/siliconcarbide stack. The first spacer layer 140 may be formed using CVD, PVD,ALD, the like, and/or combinations thereof.

FIG. 1C illustrates patterning of the first spacer layer 140. Thepatterning process removes horizontal portions of the first spacer layer140 while remaining vertical portions of the first spacer layer 140around the resistance switching element 132 and the top electrode 134.The remaining portions of the first spacer layer 140 can be referred toas spacers 142. In some embodiments, the spacers 142 cover sidewalls ofthe resistance switching element 132 and leave the top electrode 134 andportions of the bottom electrode layer 120 uncovered. In someembodiments, the patterning of the first spacer layer 140 may include anetch process, such as an anisotropic etch using acceptablephotolithography techniques. The patterning process may be dry etching,wet etching, or a combination thereof. In some other embodiments, theformation of the spacers 142 may be omitted. In some embodiments wherethe first spacer layer 140 is silicon nitride, the patterning of thesilicon nitride layer includes a dry etching using CH₂F₂ as an etchant,although other applicable etchants may be used.

Reference is made to FIG. 1D. A penetration barrier layer 150 isconformally formed over the bottom electrode layer 120, around thespacers 142, and over the top electrode 134. In some embodiments, thepenetration barrier layer 150 may act as an etch resistant layer againstone or more subsequent etching processes. The penetration barrier layer150 may be a metal oxide layer different from materials of the spacers140. In some embodiments, the penetration barrier layer 150 is a metaloxide layer. For example, the penetration barrier layer 150 includesmaterials such as aluminum oxide (AlO_(x)), aluminium oxynitride (AlON),tungsten carbide (WC), titanium nitride (TiN), tantalum nitride (TaN),titanium oxide (TiO), tantalum oxide (TaO), the like, and/or acombination thereof.

Reference is made to FIG. 1E. A second spacer layer 160 is blanketformed over the penetration barrier layer 150. The second spacer layer160 may include a material different from the penetration barrier layer150. For example, the second spacer layer 160 includes suitabledielectric materials such as silicon nitride, silicon carbide,carbon-doped silicon nitride, carbon-doped silicon oxide, siliconoxynitride, and combinations thereof. In some embodiments, the secondspacer layer 160 may also be a composite layer including two or morelayers made of different materials, such as a silicon nitride/siliconcarbide stack. The second spacer layer 160 may be formed using CVD, PVD,ALD, the like, and/or combinations thereof. In some embodiments, thefirst spacer layer 140 (referring to FIG. 1B) is formed at a firsttemperature, the second spacer layer 160 is formed at a secondtemperature higher than the first temperature, such that a density ofthe second spacer layer 160 is greater than a density of the spacer 142.In other some embodiments, the second spacer layer 160 may be omitted.

FIG. 1F illustrates patterning of the second spacer layer 160. Thepatterning process removes horizontal portions of the second spacerlayer 160 while remaining portions of the second spacer layer 160 aroundthe stacks 130 and the spacers 142. The remaining portions of the secondspacer layer 160 can be referred to as spacers 162. In some embodiments,the spacers 162 cover sidewalls of the stacks 130 and expose portions ofthe penetration barrier layer 150 over the top electrode 134. In someembodiments, the spacers 162 expose portions 152 of the penetrationbarrier layer 150 over second portions 124 of the bottom electrode layer120. In some embodiments, the spacers 162 are separated due to thepatterning process.

In some embodiments, the patterning of the second spacer layer 160 mayinclude an etch process, such as an anisotropic etch using acceptablephotolithography techniques. The patterning process may be dry etching,wet etching, or a combination thereof. In some embodiments, thepenetration barrier layer 150 has higher etch resistance to an etchantused in the patterning the second spacer layer 160 than that of thesecond spacer layer 160, such that the penetration barrier layer 150protects the stack 130 and the spacers 142 from being damaged during thepatterning of the second spacer layer 160. In some embodiments where thesecond spacer layer 160 is silicon nitride, the patterning of thesilicon nitride layer includes a dry etching using CH₂F₂ as an etchant,although other applicable etchants may be used.

Reference is made to FIG. 1G. An interlayer dielectric (ILD) layer 170is formed on the resulting structure of FIG. 1F and around thepenetration barrier layer 150. The ILD layer 170 may have the samematerial as the underlying ILD layer 110. The ILD layer 170 may be anextra low-k dielectric (ELK) layer, such as carbon doped silicondioxide, may be an oxide, such as silicon oxide, and/or may be the likeor a combination thereof. In some embodiments, the ILD layer 170 may beformed of a low-k dielectric material having a k value less than about3.9. The k value of the ILD layer 170 may even be lower than about 2.8.

Reference is made to FIG. 1H. A tri-layer photoresist 200 is formed onthe interlayer dielectric (ILD) layer 170. The tri-layer photoresist 200includes a bottom layer 210, a middle layer 220, and a top layer 230. Insome embodiments, the bottom layer 210 includes a C_(x)H_(y)O_(z)material, the middle layer 220 includes a SiC_(x)H_(y)O_(z) material,and the top layer 230 includes a C_(x)H_(y)O_(z) material. TheC_(x)H_(y)O_(z) material of the bottom layer 210 may be identical to theC_(x)H_(y)O_(z) material of the top layer 230 in some embodiments, butthey may also be different in other embodiments. The top layer 230 alsoincludes a photo-sensitive element, such as a photo-acid generator(PAG). This allows a photolithography process to be performed to patternthe top layer 230. It is understood that in other embodiments, one ormore layers of the tri-layer photoresist may be omitted, or additionallayers may be provided as a part of the tri-layer photoresist, and thelayers may be formed in difference sequences.

In some embodiments, the top layer 230 is patterned by aphotolithography process, which may include one or more exposure,developing, rinsing, and baking processes (not necessarily performed inthis order). The photolithography process patterns the top layer 230into a photoresist mask, which may have one or more trenches or openingsO1 respectively over the second portions 124 of the bottom electrodelayer 120 uncovered by the stacks 130 and the spacers 142 and 162. Thetrenches or openings O1 expose the middle layer 220 therebelow. Themiddle layer 220 is then etched using the photoresist mask to form apatterned middle layer, and the bottom layer 210 is then etched usingthe patterned middle layer to form a patterned bottom layer. Thepatterned bottom layer 210 is then used to pattern the ILD layer 170. Inother some embodiments, the photoresist 200 may include a singlephotoresist layer, and the photoresist layer is patterned and then usedto pattern the ILD layer 170.

Reference is made to FIG. 1I. One or more trenches or opening O2 arethen etched in the ILD layer 170 using the photoresist 200 as an etchmask, so as to expose portions 152 of the penetration barrier layer 150over the second portions 124 of the bottom electrode layer 120. To bespecific, a portion of the ILD layer 170 over the second portion 124 ofthe bottom electrode layer 120 is removed until reaching the portion 152of the penetration barrier layer 150. In some embodiments, thepenetration barrier layer 150 has higher etch resistance to an etchantused in the removing the portion of the ILD layer 170 (or the etchingthe openings O2) than that of the ILD layer 170 and the spacers 142 and162, such that the penetration barrier layer 150 may protect the spacers142 and 162 and the bottom electrode layer 120 from being damage in theetching the openings O2. In some embodiments where the ILD layer 170 issilicon oxide, the etchant used in etching the openings O2 can be dilutehydrofluoric acid (HF), HF vapor, CF₄, C4F₈, CH_(x)F_(y), C_(x)F_(y),SF₆, or NF₃ gas. For example, in an etching process using dilute HF, HFvapor, CF₄, C₄F₈, CH_(x)F_(y), C_(x)F_(y), SF₆, or NF₃ gas as anetchant, an etch rate of the penetration barrier layer 150 is slowerthan that of at least one of the spacers 142, 162 and the ILD layer 170.After the etching process, the tri-layer photoresist 200 can be removedusing, for example, an ashing process.

Reference is made to FIG. 1J. The portions 152 of the penetrationbarrier layer 150 under the openings O2 are removed through the openingsO2 while remaining penetration barrier layers 154 over the respectivestacks 130 and the respective spacers 142. In some embodiments, theremaining penetration barrier layers 154 may be around or enclose therespective spacers 142, and the spacers 162 are around or enclose therespective remaining penetration barrier layers 154.

Then, the bottom electrode layer 120 is patterned to remove the secondportions 124 of the bottom electrode layer 120 under the openings O2 andform the bottom electrodes 126. The bottom electrodes 126 are in contactwith the metallization pattern 112. The bottom electrode layer 120 canbe patterned using the patterned ILD layer 170 as an etch mask, andhence the bottom electrode layer 120 can be patterned in a self-alignedmanner. In some embodiments, the patterning process may include one ormore etching operations, such as dry etching, wet etching or acombination thereof. In some embodiments, the patterning process mayinclude a dry etching using chlorine based, fluorine based, or oxygencontaining gaseous etchant such as CO, O₂, CO₂, CF₄, CH₂F₂, C₄F₈, NF₃,SF₆, Cl₂, BCl₃ and/or other chemicals, as example. In some embodiments,the remaining penetration barrier layers 154 have higher resistance topenetration of the chlorine based, fluorine based, or oxygen containinggaseous etchant than that of at least one of the spacers 142 and 162 andthe ILD layer 170, such that the stack 130 including the resistanceswitching element 132 may be protected from the invasion of the chlorinebased, fluorine based, or oxygen containing gaseous etchant by thepenetration barrier layer 150 during the patterning the bottom electrodelayer 120. For example, the penetration barrier layers 154 have higherresistance to penetration of chlorine, fluorine, or oxygen than that ofthe spacer layers 142, 162 and the ILD layer 170. For example, apenetration rate of chlorine, fluorine, or oxygen through thepenetration barrier layer 154 is slower than that through at least oneof the spacers 142, 162 and the ILD layer 170. As a result, thepenetration barrier layer 154 can protect the resistance switchingelement 132 against penetration of chlorine, fluorine, or oxygen.

Reference is made to FIG. 1K. An interlayer dielectric (ILD) layer 180is disposed on the resulting structure of FIG. 1J. The ILD layer 180fills the openings O2 in the ILD layer 170. The ILD layer 180 may havethe same material as the underlying ILD layers 110 and 170. The ILDlayer 180 may be an extra low-k dielectric (ELK) layer, such as carbondoped silicon dioxide, may be an oxide, such as silicon oxide, and/ormay be the like or a combination thereof.

Reference is made to FIG. 1L A portion of the ILD layer 170 and aportion of the ILD layer 180 over the top electrode 134 are removed,such that top via holes VH1 are formed in the ILD layers 170 and 180. Insome embodiments, the top via holes VH1 are etched in the ILD layers 170and 180 until reaching portions of the remaining penetration barrierlayers 154 over the top electrodes 134. In some embodiments, theremaining penetration barrier layers 154 have higher etch resistance tothe etching the top via holes VH1 than that of the ILD layers 170 and180, so that the penetration barrier layers 154 can act as etch stoplayers for stopping or slowing down the etching process of forming thetop via holes VH1. For example, in this etching process, etch rates ofthe penetration barrier layers 154 are slower than etch rates of the ILDlayers 170 and 180. In some embodiments where the ILD layers 170 and 180are silicon oxide, the etchant used in etching the top via holes VH1 canbe dilute HF, HF vapor, CF₄, C4F₈, CH_(x)F_(y), C_(x)F_(y), SF₆, or NF₃gas.

Reference is made to FIG. 1M. A portion of the remaining penetrationbarrier layers 154 exposed by the top via holes VH1 is removed, suchthat the top electrodes 134 are exposed. Then, conductors 190 are formedinto the top via holes VH1 respectively and in contact with the topelectrodes 134 respectively. The conductors 190 may include conductivematerial, such as metal. The conductors 190 may also include one or moreliner and barrier layers in additional to a metal conductor. The linerand/or barrier may be conductive and deposited using CVD or PVD. Themetal may be deposited using PVD or one of the plating methods, such aselectrochemical plating. A planarization process, such as a CMP process,is then performed to planarize the conductors 190 and the ILD layer 180.

As illustrated in FIG. 1M, a memory device includes a bottom electrode126, a resistance switching element 132, a top electrode 134, an ILDlayer 170, spacers 142 and 162, and a penetration barrier layer 154 isformed. The resistance switching element 132 is sandwiched between thebottom electrode 126 and the top electrode 134. The ILD layer 170surrounds the resistance switching element 132. The spacers 142 and 162are between the ILD layer 170 and a sidewall of the resistance switchingelement 132. The penetration barrier layers 154 is between the ILD layer170 and the sidewall of the resistance switching element 132, andthereby protect the resistance switching element 132 from thepenetration of etchant used in patterning the bottom electrode layer. Insome embodiments, the penetration barrier layer 150 may also act as anetch stop layer for various etching processes, such as the etchingprocesses as shown in FIGS. 1F, 1I and 1L.

FIGS. 2A through 2B are cross-sectional views of an integrated circuitin various stages of fabrication in accordance with some embodiments ofthe present disclosure. As illustrated in FIG. 2A, in some condition,the trenches or openings O1 of the top layer 230 of the tri-layerphotoresist 200 (referring to FIG. 1H) are misaligned with the secondportions 124 of the bottom electrode layer 120 uncovered by the stacks130 and the spacers 142 and 162 due to poor overlay (OVL) control, suchthat the etching the openings O2 may further etching portions of thespacers 162. However, since the penetration barrier layer 150 has higheretch resistance against the etching the openings O2 compared with thespacers 162, vertical portions of the penetration barrier layer 150 atinner sides of the spacers 162 will not be removed by this etchingprocess, so that the inner spacers 142 and the stacks 130 can beprotected from the etching process even if the outer spacers 162 areunexpectedly removed due to the photolithographic misalignment.Therefore, OVL control in the photolithography process can be relaxed,which means the process window of the photolithography process can beenlarged.

FIG. 2B shows the portion 152 of the penetration barrier layer 150 andthe second portion 124 of the bottom electrode layer 120 are removedthrough the opening O2, while leaving remaining penetration barrierlayers 154 and bottom electrodes 126 over the substrate 100. In someembodiments, the patterning process are described in the foregoingcontext and thus not described herein for clarity.

FIG. 3 is a cross-sectional view of another integrated circuit inaccordance with some embodiments of the present disclosure. This ICshares some of the features of the IC as illustrated in FIG. 1M. Forexample, the IC may include a substrate 100 and ILD layers 110, 170 and180 as described above. Additionally, a penetration barrier layer 254may be formed in contact with a sidewall of the stack 130, and thespacers 142 and 162 are concentrically arranged around the penetrationbarrier layer 254. The penetration barrier layer 254 is a metal oxidelayer and includes materials such as aluminum oxide (AlO_(x)), aluminiumoxynitride (AlON), tungsten carbide (WC), titanium nitride (TiN),tantalum nitride (TaN), titanium oxide (TiO), tantalum oxide (TaO), thelike, and/or a combination thereof.

FIG. 4 is a cross-sectional view of another integrated circuit inaccordance with some embodiments of the present disclosure. This ICshares some of the features of the IC as illustrated in FIG. 1M. Forexample, the IC may include a substrate 100 and ILD layers 110, 170 and180 as described above. Additionally, a penetration barrier layer 354may be formed concentrically around the spacers 142 and 162. Thepenetration barrier layer 354 is a metal oxide layer and includesmaterials such as aluminum oxide (AlO_(x)), aluminium oxynitride (AlON),tungsten carbide (WC), titanium nitride (TiN), tantalum nitride (TaN),titanium oxide (TiO), tantalum oxide (TaO), the like, and/or acombination thereof.

Other details of the present embodiments are similar to that of theembodiments of FIG. 1M, and therefore omitted herein.

FIG. 5 illustrates an integrated circuit in accordance with someembodiments. The integrated circuit includes a logic region 900 and amemory region 910. The logic region 900 may include circuitry, such asan exemplary logic transistor 902, for processing information receivedfrom memory cells 920 in the memory region 910 and for controllingreading and writing functions of memory cells 920. In some embodiments,the memory cell 920 may include a bottom electrode 922 and a topelectrode 926, with a resistance switching element 924 sandwiched inbetween the bottom and top electrodes 922 and 926. Penetration barrierlayers 930 are around sidewalls of the memory cell 920, respectively.Spacers 940 may be between the penetration barrier layers 930 and thesidewalls of the memory cell 920, respectively. Spacers 950 may bearound the penetration barrier layers 930, respectively.

As depicted, an exemplary integrated circuit is fabricated using fivemetallization layers, labeled as M1 through M5, with five layers ofmetallization vias or interconnects, labeled as V1 through V5. Otherembodiments may contain more or fewer metallization layers and acorresponding more or fewer number of vias. Logic region 900 includes afull metallization stack, including a portion of each of metallizationlayers M1-M5 connected by interconnects V2-V5, with V1 connecting thestack to a source/drain contact of the logic transistor 902. The memoryregion 910 includes a full metallization stack connecting the memorycells 920 to transistors 912 in the memory region 910, and a partialmetallization stack connecting a source line to the transistors 912 inthe memory region 910. The memory cells 920 are depicted as beingfabricated in between the M4 layer and the M5 layer. Also included inintegrated circuit is a plurality of ILD layers. Six ILD layers,identified as ILD0 through ILD5 are depicted in FIG. 5 as spanning thelogic region 900 and the memory region 910. The ILD layers may provideelectrical insulation as well as structural support for the variousfeatures of the integrated circuit during many fabrication processsteps.

Based on the above discussions, it can be seen that the presentdisclosure offers advantages. It is understood, however, that otherembodiments may offer additional advantages, and not all advantages arenecessarily disclosed herein, and that no particular advantage isrequired for all embodiments. One advantage is that the penetrationbarrier layer around the resistance switching element has higherresistance to penetration of the chlorine based or fluorine basedetchant than that of the spacers and the ILD layer, such that thepenetration barrier layer protects the resistance switching element fromthe invasion of the etchant during the patterning the bottom electrodelayer. Another advantage is that the penetration barrier layer may havehigher etch resistance to the spacers and the ILD layers, such that thepenetration barrier layer may also act as an etch stop layer in theetching the spacer layers or the ILD layers.

According to some embodiments of the present disclosure, a methodincludes depositing a bottom electrode layer, a resistance switchingelement layer, and a top electrode layer over a first dielectric layer;etching the top electrode layer and the resistance switching elementlayer to form a resistance switching element over the bottom electrodelayer and a top electrode over the resistance switching element;depositing a metal-containing compound layer over the top electrode, theresistance switching element, and the bottom electrode layer; andetching the metal-containing compound layer and the bottom electrodelayer to form a bottom electrode over the first dielectric layer.

According to some embodiments of the present disclosure, a methodincludes depositing a bottom electrode layer, a resistance switchingelement layer, and a top electrode layer over a first dielectric layer;etching the top electrode layer and the resistance switching elementlayer to form a resistance switching element over the bottom electrodelayer and a top electrode over the resistance switching element;depositing a first spacer layer over the top electrode, the resistanceswitching element, and the bottom electrode layer; etching the firstspacer layer to form a first spacer surrounding the resistance switchingelement; and forming a metal-containing compound layer extending along asidewall of the first spacer.

According to some embodiments of the present disclosure, a methodincludes forming a top electrode and a resistance switching element overa bottom electrode layer, wherein the top electrode is over theresistance switching element; depositing a metal-containing compoundlayer over the top electrode, the resistance switching element, and thebottom electrode layer; depositing a first dielectric layer over themetal-containing compound layer; etching the first dielectric layer andthe metal-containing compound layer to form a via hole that exposes thetop electrode; and filling the via hole with a conductor.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method, comprising: depositing a bottomelectrode layer, a resistance switching element layer, and a topelectrode layer over a first dielectric layer; etching the top electrodelayer and the resistance switching element layer to form a resistanceswitching element over the bottom electrode layer and a top electrodeover the resistance switching element; depositing a metal-containingcompound layer over the top electrode, the resistance switching element,and the bottom electrode layer, wherein a bottom surface of themetal-containing compound layer is in contact with a top surface of thebottom electrode layer; and etching the metal-containing compound layerand the bottom electrode layer to form a bottom electrode over the firstdielectric layer.
 2. The method of claim 1, further comprising: prior todepositing the metal-containing compound layer, depositing a spacerlayer over the top electrode, the resistance switching element, and thebottom electrode layer; and etching the spacer layer to form a spacersurrounding the resistance switching element.
 3. The method of claim 2,wherein etching the spacer layer is performed such that a top of thespacer is higher than a bottom of the top electrode.
 4. The method ofclaim 1, further comprising: prior to etching the metal-containingcompound layer and the bottom electrode layer, depositing a spacer layerover the metal-containing compound layer; and etching the spacer layerto form a spacer disposed along a sidewall of the metal-containingcompound layer.
 5. The method of claim 4, further comprising: prior toetching the metal-containing compound layer and the bottom electrodelayer, etching the spacer to expose a portion of the metal-containingcompound layer.
 6. The method of claim 4, wherein etching the spacerlayer to form the spacer is performed such that a top of themetal-containing compound layer is higher than a top of the spacer. 7.The method of claim 1, further comprising: prior to etching themetal-containing compound layer and the bottom electrode layer,depositing a second dielectric layer over the metal-containing compoundlayer; and prior to etching the metal-containing compound layer and thebottom electrode layer, etching the second dielectric layer to expose aportion of the metal-containing compound layer, wherein etching themetal-containing compound layer comprises etching the exposed portion ofthe metal-containing compound layer.
 8. The method of claim 7, furthercomprising: after etching the metal-containing compound layer and thebottom electrode layer, depositing a third dielectric layer over thefirst dielectric layer and the second dielectric layer.
 9. The method ofclaim 8, further comprising: etching the third dielectric layer, thesecond dielectric layer, and the metal-containing compound layer to forma via hole that exposes the top electrode; and filling the via hole witha conductor.
 10. The method of claim 9, wherein etching the thirddielectric layer, the second dielectric layer, and the metal-containingcompound layer is performed such that a bottom of the via hole is lowerthan a top of the metal-containing compound layer.
 11. A method,comprising: depositing a bottom electrode layer, a resistance switchingelement layer, and a top electrode layer over a first dielectric layer;etching the top electrode layer and the resistance switching elementlayer to form a resistance switching element over the bottom electrodelayer and a top electrode over the resistance switching element;depositing a first spacer layer over the top electrode, the resistanceswitching element, and the bottom electrode layer; etching the firstspacer layer to form a first spacer surrounding the resistance switchingelement; forming a metal-containing compound layer extending along asidewall of the first spacer; and patterning the bottom electrode layerinto a bottom electrode, such that the bottom electrode is below bottomsof the resistance switching element and the first spacer and extendingbeyond an entire width of a combination of the resistance switchingelement and the first spacer.
 12. The method of claim 11, whereinforming the metal-containing compound layer is performed such that a topof the metal-containing compound layer is higher than a top of the firstspacer.
 13. The method of claim 11, further comprising: depositing asecond spacer layer over the metal-containing compound layer; andetching the second spacer layer to form a second spacer disposed along asidewall of the metal-containing compound layer.
 14. The method of claim11, wherein forming the metal-containing compound layer is performedsuch that the metal-containing compound layer has a portion extendingalong a top surface of the bottom electrode layer.
 15. The method ofclaim 14, further comprising: depositing a second spacer layer over themetal-containing compound layer; and etching the second spacer layer toform a second spacer over the portion of the metal-containing compoundlayer that extends along the top surface of the bottom electrode layer.16. The method of claim 15, wherein etching the second spacer layer isperformed such that the portion of the metal-containing compound layerthat extends along the top surface of the bottom electrode layer extendsbeyond an entire width of a bottom surface of the second spacer.
 17. Amethod, comprising: forming a top electrode and a resistance switchingelement over a bottom electrode layer, wherein the top electrode is overthe resistance switching element, and the bottom electrode layer has afirst portion below the resistance switching element and a secondportion free of coverage of the resistance switching element; depositinga metal-containing compound layer over the top electrode, the resistanceswitching element, and the first and second portions of the bottomelectrode layer; depositing a first dielectric layer over themetal-containing compound layer; etching the first dielectric layer andthe metal-containing compound layer to form a via hole that exposes thetop electrode; and filling the via hole with a conductor.
 18. The methodof claim 17, further comprising: prior to etching the first dielectriclayer and the metal-containing compound layer to form the via hole,depositing a second dielectric layer over the first dielectric layer,wherein etching the first dielectric layer and the metal-containingcompound layer to form the via hole comprises etching the seconddielectric layer.
 19. The method of claim 17, wherein filling the viahole with the conductor is performed such that the conductor is incontact with the metal-containing compound layer.
 20. The method ofclaim 17, wherein etching the first dielectric layer and themetal-containing compound layer is performed such that a top of themetal-containing compound layer is higher than a top of the topelectrode after etching the first dielectric layer and themetal-containing compound layer.